The present invention concerns a high voltage supply system of a load, this load being able to be, more particularly, an X-ray generator for medical or industrial application. The invention concerns more particularly a simplification of the voltage adjustment and regulation means applied to the load, as well as a reduction in the residual undulation ratio of this voltage.
A high voltage supply system of an X-ray generator essentially constituted by a rectifier bridge, by a resonance type thyristor-inverter supplied by the rectifier bridge and by adjustment and regulation means admitting as error voltage a signal representative of the voltage applied to the terminals of the load is already known. In this type of system, it is difficult to cause to vary the voltage supplied to the load through the entire range of variations required. By way of example, a system comprising two adjustment and regulation loops has been proposed, one of the loops acting on the rectifier bridge in order to vary the value of the direct voltage applied to the inverter; the other loop acting on the operating frequency of the inverter. The first adjustment and regulation loop thus allows a rough voltage adjustment whereas the second allows a fine adjustment. Such a system is described in detail in French patent No. 2 451 149 (Also U.S. Pat. No. 4,295,049).
This system is complicated since it requires two adjustment and regulation loops. Furthermore, the rectifier bridge must be equipped with thyristors, or similar switchover components, that are expensive components. Furthermore and above all, there is a real drawback in causing to vary the frequency of the inverter. Indeed, its operating is optimal when the oscillating frequency is selected slightly lower than the resonance frequency of an oscillating circuit including the primary winding of the raising transformer of this inverter. By decreasing the operating frequency with respect to this optimal value, it is effectively possible to cause to decrease, within a limited range, the output voltage supplied by the inverter (which is done by the second adjustment and regulation loop mentioned herein above), but at the expense of a notable increase in the residual undulation of the direct current voltage applied to the X-ray generator.